53418-18-1Relevant articles and documents
Reduction of metal carbonyls via electron transfer. Formation and chain decomposition of formylmetal intermediates
Narayanan,Amatore,Kochi
, p. 926 - 935 (1986)
Electron transfer to metal carbonyls such as Cr(CO)6 and Fe(CO)5 affords the corresponding 19-electron anion radicals which undergo facile hydrogen atom transfer with trialkyltin hydrides. The yields of the resultant formylmetal carbonyls are limited by a radical-chain decomposition, the mechanism of which is established by a detailed study of the formyldirhenate complex (OC)5ReRe(CO)4CHO-Bu4N+ (IV). The chain process in Scheme I leading to the hydridodirhenate V is induced either thermally by azo initiator or photochemically with light of λ > 400 nm. High kinetic chain lengths and quantum yields of >300 are measured. Reductive methods involving initiation at an electrode surface or with sodium anthracene also promote the chain decomposition, but the turnover numbers are limited. Detailed kinetics analysis of the cyclic voltammetric data reveals the presence of two mechanistic pathways - one involving a radical-chain process (Scheme I) and the other an electron-transfer process (Scheme II). The radical-chain process for the decomposition of formylmetals is retarded by hydrogen atom donors. The latter is shown by the unusual stabilization of a variety of formylmetal species that are otherwise quite transient. Synthesis and decomposition of formylmetals by homolytic mechanisms involving facile hydrogen atom transfers are thus microscopically related processes.
Group- and electron-transfer reactions of tetracarbonylferrate(2-)
Zhen, Yueqian,Atwood, Jim D.
, p. 2778 - 2780 (2008/10/08)
Reactions of Fe(CO)42- with metal carbonyl complexes lead to distinct mechanisms. Reaction with metal carbonyl cations gives a two-electron process that we interpret as a CO2+ transfer. Reaction with Mn2(CO)10 occurs by a single-electron transfer producing Fe2(CO)82- and Mn(CO)5-. Reaction with Mn(CO)5Br also occurs by a single-electron transfer. Reaction with Re(CO)5Br could be either SET or direct nucleophilic displacement. Kinetic studies are reported for several reactions.
Electroreduction of carbonylmanganese(I) cations. Mechanism of ligand substitution and hydride formation via manganese(0) intermediates
Narayanan,Amatore,Kochi
, p. 129 - 136 (2008/10/08)
Hydridomanganese(I) complexes (OC)3MnL2H are the principal products from a series of acetonitrile derivatives of carbonylmanganese cations, i.e., (OC)3Mn(NCMe)nL3-n+ (I), when the reductions are carried out electrochemically in the presence of added phosphines L. Cyclic voltammetric studies show that the conversion to the hydride can be formulated in three discrete stages. First, the carbonylmanganese cation such as (OC)3Mn(NCMe)3+ with n = 3 undergoes an electrocatalytic ligand substitution with added L to form the bis(phosphine) complex (OC)3Mn(NCMe)L2+ via labile 19-electron Mn(0) intermediates as in Scheme V. Second, the substitution product (OC)3Mn(NCMe)L2+ is reduced to the Mn(0) radical (OC)3Mn(NCMe)L2?; which is common to all cationic precursors irrespective of the degree of prior phosphine coordination in the precursor I (i.e., n = 1, 2). Third, the hydridomanganese product is derived by hydrogen atom transfer to the carbonyl ligand of the 19-electron intermediate (OC)3Mn(NCMe)L2? to form the formyl complex (OC)2Mn(NCMe)L2CHO, followed by the electrocatalytic extrusion of the coordinated ligand (MeCN) as in Scheme III. The third stage is established in the reductive conversion of the cationic (OC)4Mn(PPh3)2+ to the hydride (OC)3Mn(PPh3)2H by the observation of the intermediate (OC)3Mn(PPh3)2CHO during cyclic voltammetry. A competition to form the carbonylmanganate (OC)3MnL2- as a byproduct of reduction is also delineated.
